E: Engine Thorspark on a Comet

vibrac

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I suppose those with original dynamos trust Mr Miller dynamo more than Mr Lucas Mag what could be described as Hobson's choice :)
 

Bill Thomas

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I have a manual old type BTH on my old Comet, Been on there forever !, Racing / Road etc.
But I like Options. Cheers Bill.
 

James B

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Looks like I’m going to need to use a strobe to time up the thorspark. I’ve always used a rod down the bore to measure piston position to time the mag but that’s not going to work here

Any thoughts on where I can get a timing mark onto a comet? Best I can think of is run it without primary cover, and mark up the front pulley. Anyone got a better idea?
 

Bill Thomas

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We did it the other day, With a standard ignition, By making a mark at the points and the body, But it being half speed, It's Plus or min' a bit. Cheers Bill.
 

timetraveller

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ClevTrev used to sell a device which fitted into the big end quill position, had a CD fitted to the shaft which was scribed with degree marks and which would allow the engine to be run with oil still going to the big end and allowed one to use a stroboscope. It was a clever bit of kit. I don't know if he still has any but if not maybe someone on this forum who lives near you might still have one.
 

Tony Wilkinson

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Looks like I’m going to need to use a strobe to time up the thorspark. I’ve always used a rod down the bore to measure piston position to time the mag but that’s not going to work here

Any thoughts on where I can get a timing mark onto a comet? Best I can think of is run it without primary cover, and mark up the front pulley. Anyone got a better idea?
When I fitted mine, I removed the primary cover then used a rod to find TDC, marked the (inner) part of the rotor. Then attached a thin wire with a screw on the case and lined up with my first mark then marked the rod to find the BTDC and marked the rotor again. Line this mark up with the wire and you can fit the rotor. I checked my settings a few times before I was happy to fit the new rotor. I then fired up the bike and set with a strobe light making sure the marks lined up on full advance. It is a bit of a faf but works ok.
You can do the same thing using a timing disc but this method works ok.
 

Peter Holmes

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There are far better methods of finding TDC than a rod down the plug hole, using that method it is almost impossible to be degree perfect, Know Thy Beast gives a very good description of the best method to use.
 

timetraveller

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I agree. A stop down the plug hole and then rotate the engine both forwards and backwards till the piston hits the stop. Note the degree plate readings, split the difference, adjust the degree plate and then go back and check it at least once.
 
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